Abstract: Nursing therapies promote recovery following severe
traumatic brain injury (TBI). However, the type and dose of treatment
needed to stimulate functional plasticity have not been determined. In
this quasi-experimental study, the effects of a structured auditory
sensory stimulation program (SSP) were examined in 12 male patients,
17-55 years old, with severe TBI. SSP was initiated 3 days after injury
and continued for 7 days. Recovery was measured by comparing baseline
Glasgow Coma Scale (GCS), Sensory Stimulation Assessment Measure (SSAM),
Ranchos Los Amigos Level of Cognitive Functioning Scale (RLA), and
Disability Rating Scale (DRS) scores to ending scores between those who
received SSP and those who did not. For the intervention group a
positive recovery of function trajectory was found for mean GCS, and
there was a greater improvement in GCS and RLA scores between baseline
and discharge testing periods. DRS and SSAM scores at baseline and at
discharge were significantly different. SSP did not affect hemodynamic
or cerebral dynamic status. Early and repeated exposure to an SSP may
promote arousal from severe TBI without adversely influencing cerebral
dynamic status.

**********

Traumatic brain injury (TBI) occurs in approximately 1.5 million-2
million people each year in the United States, accounting for more than
500,000 hospitalizations. Although emergency care, diagnostic
technology, medical intervention, and nursing care have resulted in
increased survival following TBI, arousal and cognitive recovery are not
guaranteed. More than 90,000 of those persons who are hospitalized with
TBI suffer injuries of such magnitude that long-term cognitive,
behavioral, and emotional impairments prevent them from pursuing active
and responsible lives after injury (National Institutes of Health [NIH]
Consensus Development Panel, 1999).

Cope and Hall (1982) determined that early rehabilitation after
brain injury produced better outcomes. With the current state of
knowledge related to activation of recovery mechanisms immediately
following brain injury, it can be argued that early environmental
stimuli via a sensory stimulation program may enhance recovery processes
such as plasticity, which is demonstrated as increased arousal in
comatose patients. The purpose of this study was to examine behavioral
effects of a structured sensory stimulation program (SSP) on arousal in
patients with TBI who were in coma. The specific research questions
addressed were (a) Will there be an increase in arousal between initial
assessment (baseline) and discharge assessment scores as measured by the
Glasgow Coma Scale (GCS), Sensory Stimulation Assessment Measure (SSAM),
Ranchos Los Amigos Level of Cognitive Functioning Scale (RLA), and
Disability Rating Scale (DRS) in patients who receive an auditory
sensory stimulation program? and (b) What is the effect of an auditory
sensory stimulation program on cerebral hemodynamic status (intracranial
pressure) [ICP]) and cardiopulmonary status (i.e., heart rate [HR],
respiratory rate [RR], and mean arterial pressure [MAP])?

Background

A profound sequelae of severe TBI, coma is often seen in critically
ill brain-injured patients. Coma is defined as an unarousable,
unresponsive state without eye opening, verbalization, or ability to
follow commands (Jennett & Teasdale, 1981; Plum & Posner, 1980).
Coma occurs from a variety of local or diffuse injuries that disrupt the
reticular activating system (RAS) of the brainstem. Arousal, the
foundational element of information processing, is maintained by the
RAS. Arousal is a prerequisite for the selective attention necessary for
recognizing and processing information. Without arousal, more complex
cognitive processes, such as sustained attention or concentration
necessary for learning, cannot occur (Arciniegas et al., 1999). Coma of
any duration disrupts arousal mechanisms and interferes with the
person's ability to respond to environmental stimuli. Coma of
increased duration (>24 hours) has been linked to poor recovery and
impaired functional outcomes (Gennarelli, et al. 1982).

Brain injury, although initiated at the moment of impact, is a
process that evolves over hours and weeks (Gennarelli, 1997; Povlishock
& Christman, 1995). Moreover, there is a growing body of knowledge
from the fields of medicine, psychology, and neuroscience that recovery
processes are activated immediately following TBI (McIntosh, Juhler,
& Weiloch, 1998). One such recovery process, plasticity, allows the
mature brain to modify its organization and function (Bach-y-Rita,
1990). Evidence of plasticity has been noted throughout the nervous
system and includes neurochemical, receptor, and structural changes.
Changes related to plasticity appear as dendritic branching, an increase
in the number of receptor sites, changes in the configuration of
synapses, and formation of new synapses (i.e., synaptogenesis; Kolb
& Gibb, 1991; Stein, 1994).

Enhancement of plasticity is known to occur through both endogenous
factors, such as the release of nerve growth factor (McDermott et al.,
1997; McIntosh et al., 1998), and exogenous factors, such as
environmental stimulation. The use of environment to enhance plasticity
and improve neurological function has been extensively studied in animal
models of injury and ischemia (Dalrymple-Alford & Kelche 1985;
Galani, Jarrard, Will, & Kelche, 1997).

The direct effect of environment on plasticity in human studies is
more difficult to determine. There is substantial but indirect evidence
that environmental stimulation can be used in an intervention to improve
cognitive function and produce behavioral change in humans. One such
clinical intervention, sensory stimulation, uses environmental stimuli
as a means to improve arousal in comatose, brain-injured patients. The
clinical use of stimulation programs with comatose patients has garnered
some success (Kater, 1989; LeWinn & Dimancescu, 1978; Mackay,
Berstein, Chapman, Morgan, & Milazzo, 1992; Mitchell, Bradley,
Welch, & Britton, 1990; Radar, Alston, & Ellis, 1989; Wilson,
Powell, Elliots, & Thwaites, 1991). Although reported improvements
in arousal following the implementation of a sensory stimulation program
are pro,sing, the scientific methods and procedures have differed so
significantly from study to study that interpretation and generalization
of results are difficult.

Sensory stimulation has also been examined for its effects on
cerebral dynamics. The use of auditory stimulation as a single
stimulation modality has been studied with respect to its effects on ICP
and cerebral perfusion pressure (CPP). The effect of auditory stimuli on
ICP and CPP, using a variety of auditory configurations including
familiar and unfamiliar voices, music, and environmental noise, has
yielded controversial results. Mitchell and Mauss (1978) described
increases in ventricular fluid drainage with patients who were exposed
to conversations related to their condition but little change in
drainage during routine conversation. Snyder (1983) described changes in
ICP during conversations about the patient; however, other nursing care
activities were occurring simultaneously. Consequently the actual effect
of conversation was difficult to determine. In contrast, Prins (1989)
found there was no significant effect on ICP with verbal and tactile
interactions of family members. The work of Trealor, Nalli Guin, and
Gary (1991) suggested that neither familiar nor unfamiliar voices
significantly change ICP. Johnson, Omery, and Nikas (1989) documented no
significant change in ICP during emotionally referenced conversation but
found a significant decrease in ICP during times when conversation was
unrelated to the patient. Schinner et al. (1995) demonstrated no
significant effects on ICP and CPP during three types of auditory
stimuli including music, environmental noise from the intensive care
unit, and use of earplugs. Sisson (1990) examined behavioral and
electroencephalogram (EEG) changes with auditory stimulation in
brain-injured patients with GCS scores between 4 and 8. The study
reported behavioral changes such as eye opening and extremity movement
as well as EEG changes. However, these changes were not consistent
across patients. Overall, these studies indicate that auditory stimuli
may not be a significant factor in ICP and CPP changes. These results
are based on the assumption that hearing pathways are intact following
severe traumatic injury.

Methodology

Design and Sample

Before data collection was initiated, this study was reviewed and
approved by the institutional review boards at the medical centers where
the study was conducted. A repeated measures pre- and posttest design
with an intervention and control group was used for this study. In this
quasi-experimental study, a purposive sampling technique was used.
Participants were selected based on the specific criteria discussed
below and purposively assigned to the intervention or control group.

Males were chosen for this study because they represent the group
most likely to sustain a brain injury. The age range, 17-55 years,
represents an age range documented to experience traumatic injury
(Baker, O'Neill, & Haddon, 1974). Intervention participants
were enrolled first, followed by control group participants. This
approach was taken, rather than random assignment, to eliminate
perceived differences in care between groups by family members who
potentially used the same waiting room and often shared stories.

Participants were enrolled in the study a minimum of 3 days after
sustaining brain injury if they had a GCS score of [less than or equal
to] 8 (Teasdale, & Jennett, 1974) and had stable ICE which was
defined as [less than or equal to] 20 mm Hg for 24 hours prior to entry
into the study. An RLA score (Malkamus, Booth, & Kodimer, 1980)
between Level I and Level III, which identified them as being either
unresponsive to sensory stimuli or responding at a low or inconsistent
level to sensory stimuli, was required.

Brainstem auditory evoked responses (BAERs) and EEGs were obtained
prior to commencement of stimulation and at the end of the study. BAER
was required to document that auditory pathways were intact. The pre-and
postintervention EEGs were used to examine changes in electrical
responses from baseline (i.e., the time participant was enrolled) to
completion of the study. The BAERs and EEGs were performed by a trained
EEG technician following the guidelines of the respective neurology
departments. An attending neurologist interpreted all BAER and EEG
results. Only patients with normal BAERs were enrolled in the study.

Once participants were identified as potential candidates for the
study, they were followed daily until they met the clinical parameters
for enrollment (i.e., 72 hours after injury and stable ICP for [less
than or equal to] 24 hours). Family members were approached for consent
when the participant met the clinical criteria for eligibility. BAERs
and EEGs were performed after informed consent was obtained.

GCS is a composite score used to assess neurological function and
level of arousal (Teasdale & Jenett, 1974). GCS is based on the
numerical value assigned to an individual's best eye opening,
verbal, and motor responses. Each response is scored separately and then
totaled. Scores range from 3 to 15, with 3 indicating severe
neurological deficits (i.e., severe coma) and 15 representing no
deficits (i.e., awake, alert, and oriented). Interrater reliability
using the Pearson's r = 0.95 and Cronbach's alpha 0.069 (p
< .0001) has been reported (Segatore & Way, 1992). An increase in
baseline and discharge scores represented a change in arousal.

Ranchos Los Amigos Level of Cognitive Functioning Scale. RLA
(Malkamus et al., 1980) is an eight-level behavioral rating scale used
to evaluate cognitive function based on behavioral responses to patients
with varying stages of arousal. The scale represents the progression of
recovery of cognitive structures as demonstrated through behavioral
change. The RLA score is recommended for use in determining level of
function within normally and random fluctuating environments and within
structured settings where environmental stimuli are purposefully
manipulated (Malkamus et al.). A high degree of interrater reliability
has been documented using this instrument. For the purposes of this
study, an increase in RLA score between baseline and discharge
represented a change in arousal.

Disability Rating Scale. DRS (Rappaport et al., 1982) is a
six-category functional outcome measure used to determine brain injury
recovery. Scores range from 0 (complete recovery) to 30 (death).
Reliability and validity have been established (Rappaport et al.). A
decrease in score between baseline and discharge scores represented a
change in arousal.

Sensory Stimulation Assessment Measure. SSAM (Radar et al., 1989)
is an objective measure of the responsiveness of brain-injured patients
between RLA I and IV. Stimuli are presented to five senses, and best
response is measured using a sensory stimulation response scale (SSRS).
SSRS measures the intensity of the responses to stimuli within three
categories: eye opening, motor, and vocalization. In each of the three
categories, six behavioral response choices can be selected, ranging
from no response to able to follow commands or communicate ideas. Scores
in each of the three categories are summed (range 3-36) to determine a
response score. A general responsiveness score is calculated by summing
the scores from each of the five senses. Test-retest reliability of the
scale was 0.93 with an interrater reliability of 0.89. Concurrent
validity of SSAM as a measure of sensory responsiveness was established
using RLA, GCS, and DRS. Responses to stimuli were recorded using a
modification of the grading scale developed by Radar et al. (1989),
which provided a 6-point scale for best verbal, motor, and eye
responses. SSRS scores were obtained for all categories during all
stimulation sessions (up to eight times/day), allowing for calculation
of individual responsiveness to each stimuli by time, day, and across
time.

Injury Severity Score. ISS is a calculated score of injury based on
the site and severity of anatomical injury (Baker et al., 1974). Scores
range from 1 to 75, with scores of 15 or greater considered severe
injury.

Postinjury day and admission to the study. Postinjury day (PID)
begins with admission to the hospital. Admission to the study was based
on ICP; an ICP < 20 mm Hg for 24 hours after the third PID was
required.

To ensure safety and to prevent untoward effects in this critically
ill sample, the study protocol included monitoring of clinical
parameters: MAP, ICP, CPP, HR, and RR. Clinical parameters were recorded
before and after each intervention. Demographic features of the sample
also were collected: age, mechanism of injury, hospital discharge
disposition, type of brain injury, and other anatomical injuries. An ISS
was calculated to determine the overall magnitude of the traumatic
injury. PIDs, beginning with day of injury through completion of the
study, were tracked for all participants.

The independent variable was a unimodal (auditory only) sensory
stimulation intervention. The categories of auditory stimulation varied
and represented a wide range of tone frequencies (e.g., claps, bells,
and music), diverse voice patterns (familiar and unfamiliar), and
messages requiring simple (orientation phrases) to complex
interpretative processes (commands). Families and friends of patients in
the intervention group were encouraged to participate; their
interactions served as familiar voices. They were guided in recording a
personal family message that was used during those times when they were
not present to interact with the patient.

For the intervention group the type and duration of the stimuli
stayed constant, but the sequence of delivery and the number of
stimulation sessions varied daily based on visitation time of family and
friends, participant involvement in procedures and diagnostic tests, and
physiologic stability (Table 1). All auditory stimuli (e.g., claps and
bells, music, familiar voices, orientation and command phrases, and
radio or television) were provided at least once each day, but the
session time was randomly assigned.

Procedure

After participants were identified as potential candidates for the
study, they were followed daily until they met the clinical parameters
for enrollment. Family members were approached for consent when the
participant met the clinical criteria for eligibility. BAERs and EEGs
were performed after informed consent was obtained. For all
participants, arousal, cognitive, behavioral, and outcome measures were
recorded at the beginning of the study and at the completion of the
study. Participants in both the intervention and control groups received
routine nursing care and rehabilitation services consistent with the
standard of care for TBI patients provided in the hospital. Procedures
for the intervention and control groups were as follows.

The structure of the intervention program was similar for all
participants. Stimuli were delivered each day for up to 7 days.
Participants received 5-8 stimulation sessions per day (between 8 am and
5 pm). Daylight hours were chosen to keep stimuli (aimed at arousal)
consistent with normal waking hours. The minimal interval between
sessions was 1 hour and a session duration was 5-15 minutes, depending
upon the type of stimuli (Table 1). Prior to and following each
stimulation session, the clinical parameters (i.e., MAP, ICE CPP, HR,
and RR), the arousal measures (i.e., GCS score and RLA level), and the
behavioral responses (i.e., SSAM) were recorded. SSP was discontinued if
the patient began to follow commands or demonstrated cognitive change
beyond a RLA Level III. SSP was postponed if dire medical complications
arose and restarted after the medical emergency had been resolved. For
the control group, only hourly GCS and RLA scores were collected.

Analysis

Change in arousal, the primary dependent variable, was analyzed
based on numerical change in GCS score, SSAM, RLA, and DRS scores.
Changes in the SSAM, RLA, and DRS scores (i.e., difference between
baseline and termination of study scores) were calculated and analyzed
by using the Student's t test. Daily mean GCS scores were
calculated for each group, analyzed across time using repeated measures
analysis of variance, and compared for changes.

For the intervention group, the effect of stimulation, measured by
eye/motor responses, was evaluated over time based on PID, stimulation
type (e.g., family, music, orientation), and PID by stimulation type.
The effect of stimulation on clinical variables including ICP, HR, RR,
and MAP were analyzed over time to determine interactions by PID,
stimulation type, and PID by stimulation type.

Results

Twelve male patients hospitalized for severe TBI were enrolled in
the study and assigned to either the intervention (n = 9) or control (n
= 3) groups. Patients suffered closed head injuries of all types (Table
2). The patients ranged in age from 17 to 55 years. The sample was not
statistically different between groups for age, injury severity score,
and baseline GCS Score (Table 3). Motor vehicle collision was the most
frequent injury mechanism. Two falls and one assault accounted for the
remaining participants. Control group patients were admitted to the
study an average of 2.7 PIDs earlier than the intervention group
participants. All members of the intervention group were discharged from
the medical centers to a rehabilitation facility. Two of the control
group members were discharged to a rehabilitation facility, and one was
discharged to a nursing home.

The pre-post GCS change score demonstrated marked improvement
between groups; however, these scores were not statistically significant
(intervention group = 3.3; control group = 1.0; p = .14). The mean daily
GCS scores analyzed over time were also not statistically different
between groups, but an interesting trajectory pattern emerged between
groups. The mean daily GCS scores for the intervention was lower (6.1)
and rose (6.8) over time compared to the mean daily GCS score of the
control group, which began higher (7.4) and decreased over time (6.0).
Difference between groups on SSAM scores, before and after the second
clinical measure for arousal, was statistically significant (t = -3.03;
p = .015; Table 4).

The RLA change in score for the intervention group before and after
stimulation was 1.2, but no change in score was found in the control
group (Table 4). The DRS score, a measure of functional ability,
improved from baseline to discharge in the intervention group (18.8 to
15.1), compared to the control group (19.3 to 19.0) as reflected by the
decreasing scores. The DRS change score stimulation indicated a
statistical difference between groups (p = .0005; Table 4).

Combined eye and motor (EM) responses of participants receiving the
sensory stimulation program were evaluated to determine whether an
interaction effect occurred over time by PID, stimulation type (family
voices, music, and orientation) or PID by stimulation type. Because the
sensory stimulation program was started after 24 hours of stable ICP,
the number of days between the injury and admission to the study was
different for each participant. Thus, analysis of the effect of
stimulation on EM responses was performed for each participant.

Several participants demonstrated significant responses (Table 5).
Four participants (44%) had EM changes that were significant across
PIDs. One participant with significant EM changes by PID also
demonstrated a stimulation preference and had a significant PID by
stimulation type effect. Analysis of variance revealed a significant
difference in response to family stimuli (p = .043) and music (p =
.023). Although this finding was not significant when the three types of
stimuli were combined and compared to EM change scores, two participants
demonstrated a significant response to a specific type of stimuli. One
patient responded to music (p = .04), and another responded to family
stimuli (p; .03).

To ensure safety and to prevent untoward effects in this critically
ill sample, the study protocol included monitoring of ICP, HR, RR, and
MAP before and after each intervention (Table 6). Of the nine
participants enrolled in the intervention group, only four participants
(44%) continued to have ICP monitors in place at the time of the
intervention. In this group of participants, ICP changes were recorded
after stimulation (range of change 1-5 mm Hg), but the increases were
not statistically or clinically significant in any of the cases.
Increases in ICP were not related to PID or stimulation type.

Data for HR, RR, and MAP were collected on all nine participants
and were examined across injury days, before and after stimulation, and
by stimulation type (Table 6). Five participants (55%) had significant
changes across time for HR, and two (22%) had statistically significant
changes by stimulation type. Six participants (66%) had significant
changes across time for RR, and one patient (11%) had a significant
difference in RR by stimulation type. Three participants (33%) had a
significant change in MAP across time. These responses were isolated
changes in cardiopulmonary status, but they were not accompanied by
change in medical status nor did they require termination or
postponement of the stimulation program; thus they were deemed to be of
little clinical significance.

Discussion

The aim of this study was to measure increases in arousal in
comatose patients using an auditory sensory stimulation program, which
controlled for intact auditory pathways using BAERs. In this study, an
auditory SSP was safely administered to a critically ill group of
participants, and a positive trajectory of improvement was demonstrated
in those participants who received SSP.

The mean time for entry into the study was 9.4 days after injury
for the intervention group and 6.0 days for the control group. The
intervention group was admitted to the study 3.4 days later than the
control group. The delay in eligibility for enrollment in the study was
related to continued elevations of ICE There is no way to determine from
these data whether the delay in entry to SSP was a benefit (provided
brain recovery time) or a detriment (prolonged brain injury time),
because both recovery and injury were occurring simultaneously (McIntosh
et al., 1998).

The lack of unequivocal support for the use of sensory stimulation
programs following TBI is related to the small sample. The small sample
size does not provide the power necessary to suggest an interaction
effect that was greater than normal recovery from a brain injury. It can
only be inferred that those who received the SSP had an upward trend in
arousal.

Although this study lacks the sample size necessary for robust
statistical analysis, the improvement in arousal following a unimodal
(auditory) sensory stimulation program early after injury was consistent
with findings reported in other studies (Kater, 1989; Mackay et al.,
1992; Mitchell et al., 1990; Radar et al., 1989; Wilson et al., 1991).
Mitchell et al. reported similar findings in patients who received a
multimodal coma arousal procedure early after sustaining brain injury (M
= 7.08 days). In contrast, Kater and Radar et al. reported improvement
in arousal using a multimodal sensory stimulation several weeks after
injury when patients had been admitted to an acute rehabilitation
program or to a nursing home.

The lack of significant findings in this report is also related to
reliance on clinical measures of arousal. Although the clinical outcome
measures used in this study and other similar studies are reliable and
valid for clinical use, they do not provide the sensitivity necessary to
measure subtle physiological changes in arousal. For example,
participants were admitted to this study between RLA levels I and III
and were discharged from the study at levels greater than Level III.
Because RLA level provides a description of general behaviors but does
not provide specific qualitative or quantitative endpoints, participants
admitted to this study at Level III and discharged at Level III
demonstrated no change in RLA level. Actually, small but critical
changes in arousal, such as increased arousal frequency or duration,
muscle tightening, and eye twitches, were occurring based on
observations and SSAM scores, but these subtle changes were not captured
by broad clinical outcome measures such as RLA level or GCS score.
Another flaw in the use of clinical measures such as GCS, DRS, and SSAM
is that they all measure the same three variables: eye opening,
vocalization, and motor response, yet the instruments differ in purpose,
scoring, and inclusion of other elements.

Measures that are sensitive to the physiological, behavioral, and
cognitive responses of comatose patients must be identified and utilized
before the effectiveness of SSPs can be judged. Such an approach also
may begin to address the classic problem of differentiating brain
recovery from intervention effect. Such a criticism is not reserved for
an SSP alone but can be applied to any clinical research related to
brain injury recovery whether in randomized clinical trials using
neuroprotective agents or rehabilitation techniques (NIH, 1999). Without
a sensitive, graded tool that measures change from baseline to
discharge, patients are categorized as failing to progress along a
continuum from coma to wakefulness. Such an outcome has significant
effects not only on research findings but also on rehabilitation
decisions made on behalf of brain-injured patients.

Unlike results reported by Wilson et al. (1991), most patients did
not show a preference for one type of auditory stimuli over another. Two
patients responded to family voices and one patient responded to music,
but these effects were not sustained and the reasons for this response
were not clear. Perhaps the type or duration of the stimuli was not
sufficient. Or it may be that the clinical measures used to determine
outcomes did not have the sensitivity and accuracy to pick up the
patients' behavioral responses. Sisson (1990) reported that
behavioral changes such as eye opening and extremity movement, as well
as EEG changes, were inconsistent among patients exposed to auditory
stimulation. Sisson attributed the inconsistencies to patient
variability rather than measure insensitivity.

Sensory stimulation is an intervention, yet the dose, duration,
type, frequency, and timing of the intervention have not been
systematically addressed in the sensory stimulation literature. Most
recommendations for devising a sensory intervention are based on
integrated reviews of literature (Davis & White, 1995; Helwick,
1994), but the overall contributions of each component within the
program have not been well tested. Radar et al. (1989) reported patients
responded best when they were placed in an upright position and exposed
to high personal contact. In this study, a unimodal stimulation method
produced behavioral responses, but responses to specific types of
stimuli were highly individualized. Duration of stimulation necessary to
evoke behavioral responses and optimal duration between sessions were
not addressed in the study but warrant further investigation.

The effects of voices and other auditory stimuli have been examined
with respect to changes in cerebrodynamic and cardiopulmonary status. An
issue related to safety is the cerebral hemodynamic and cardiopulmonary
responses during sensory stimulation. In this study, auditory
stimulation was not found to affect ICP, HR, RR, or MAP. These results
are similar to those reported by Johnson et al. (1989), Prins (1989),
Schinner et al. (1995), and Trealor et al. (1991), indicating that
auditory stimuli was not a significant factor in ICP and CPP changes.
Although no participants suffered adverse effects from stimulation in
this study, changes in medical conditions such as sepsis, paralytic
ileus, bowel obstruction, and respiratory changes occurred, and
treatments for these conditions superseded the research protocol. It is
important to be aware that undiagnosed medical problems or complications
could decrease responsiveness and thereby blunt the effect of the
sensory stimulation program. Likewise, changes in cerebrodynamic or
cardiopulmonary status could be occurring independently of the sensory
stimulation intervention, but changes in ICP or BP could inadvertently
be described as an untoward effect from the stimulation program rather
than a change in medical condition (improving or deteriorating).

Limitations and Directions for Future Research

There are several serious limitations embedded in this study The
first is the sample size. There is not sufficient power to make between-
or within-group comparisons. The second limitation is the lack of
sensitive measures for detecting subtle changes in arousal. The third
limitation is the inherent dilemma associated with the natural course of
brain injury recovery versus the plastic recovery associated with
increased stimulation.

Continued efforts to address the effects of SSP early after brain
injury are needed. Suggested areas for continued sensory stimulation
research in critically ill patients include testing a variety of
unimodal and multimodal programs for dose and duration effects,
developing outcome measures that are sensitive to subtle behavioral
changes in arousal, and performing long-term follow-up to compare
cognitive and behavioral outcomes across time.

Summary

The recent National Institutes of Health consensus conference on
"Rehabilitation of Persons with Traumatic Brain Injury"
endorsed the need for continued efforts to improve care at all levels of
recovery in order to restore functional outcome (NIH, 1999). Most of the
clinical research is fraught with complications, and an inability to
distinguish brain recovery from intervention effect is not a problem
unique to sensory stimulation research. Despite sample size and
confounding variables, participants in this study exposed to an early
SSP demonstrated a positive recovery of function trajectory without
compromising cerebral dynamic and cardiopulmonary function.

Acknowledgments

This research was supported by the National Institute for Nursing
Research #5R15NR0377302 and by the Bryan W. Robinson Foundation. Special
thanks to Soohyun Park for her assistance in preparing the manuscript.

National Institutes of Health Consensus Development Panel. (1999).
Rehabilitation of persons with traumatic brain injury: Consensus
development panel on rehabilitation of persons with traumatic brain
injury. Journal of the American Medical Association, 282, 974-983.

Questions or comments about this article may be directed to: Alice
E. Davis, PhD RN, by phone at 734/763-5650 or by e-mail at
aedavis@umich.edu. She is an assistant professor at the University of
Michigan School of Nursing, Ann Arbor, MI.